In facsimile recording it is necessary that the recorder scanning and marking mechanism which applies the facsimile signals to a moving strip of recording paper be synchronized with the facsimile signals coming into the recorder. For this synchronization it is well known to provide a framing circuit controlling the phase of a motor driving the scanning and marking mechanism. Such a framing circuit receives the synchronization pulse portion of the incoming facsimile pulse and also a corresponding framing pulse whose timing is dependent on the angular position of the scanning motor, and by comparing the time of occurrence of the framing and sync pulses adjusts the phase of the motor to bring the two pulses into coincidence or a similar relation.
One form of scanning electrode is a conductive signal marking stylus carried on a belt which conveys the stylus on two or more styli across the web along the recording zone. Examples of such belt-supported styli are found in U.S. Pat. Nos. 2,879,129 to M. Alden, 3,363,261 to K. Maiershofer and 3,369,250 to T. H. Gifft.
With such belt-supported styli a frame of graphic information is recorded by applying signals line by line to the stylus. It is necessary that each traverse of a stylus across the recording web precisely coincides with the line of signal information applied the stylus during the traverse. That is, each line of the frame of graphic information must start at the same instant the stylus starts its scan across a line of the web. If the traverse starting position of the stylus were to change from line to line in a frame some lines would be offset from others thereby distorting the graphic information in the frame or rendering it illegible.
It is an object of the present invention to provide an improved way of generating a framing pulse in a facsimile recorder using belt driven styli.